Yes Value in Noncharacter Code Point Unicode Property

Yes is the assigned value indicating that a code point is permanently reserved for internal use by applications and is never intended for interchange of text. These code points, such as U+FDD0 through U+FDEF and the last two code points of each plane, are guaranteed never to be assigned to any character, so they can be safely used as sentinels or for private signaling within a program. The value confirms that the code point should not appear in valid Unicode text streams, and any occurrence of it signifies a data error or a deliberate use outside standard interchange.